There are a multiplicity of applications in the medical sector that require affixment to the human skin by means of suitable pressure-sensitive adhesives. In view of the sensitivity of these applications, specific pressure-sensitive adhesives are employed here. These adhesives are required to meet the inherently contradictory requirements on the one hand of reliable bonding to the skin in all its variants, varying depending on the age and health condition of the patient, during application, and on the other of very substantially painless and residue-free detachment after application. Furthermore, they must not contain any substances which are sensitizing or are harmful to the skin in any other respect. Acrylate-based pressure-sensitive adhesives represent a class of adhesives frequently used in this sector. The advantage of these materials lies in their excellent adhesion, the high compatibility of the ingredients with the human skin, the low tendency toward sensitization, and the very good sterilization stability and aging resistance.
Thus EP 0 099 748 B1 describes a wound dressing based on a pressure-sensitive polyacrylate adhesive with high water vapor permeability. A disadvantage is the tendency on the part of the acrylate-based pressure-sensitive adhesives to increase bond adhesion with increasing wearing period, owing to increasing enhancement of the wetting of the skin by the pressure-sensitive adhesive. This is especially disadvantageous when the pressure-sensitively adhesive product is required, for therapeutic reasons, to spend a long time on the skin, after which it has to be removed from the skin again mechanically. In this case, in practice, there are frequent instances of injury to the skin as a result of the extraction of skin cells. In order to counter this effect, high molecular mass, pressure-sensitive acrylate adhesives are used in conjunction with plasticizing additives as adhesives for wound dressings. A solution of this kind is described, for example, in patents EP 0 891 782 B1 whose United States equivalent is U.S. Pat. No. 6,231,883 and EP 0 435 199 B1. The use of the plasticizing ingredients, in conjunction with the high molecular mass polymer matrix, produces reliable adhesion to the human skin. A disadvantageous effect here, however, is the migration tendency of the plasticizing components. This results, as a consequence of the mixing of two components having different adhesion behaviors, to nonuniform peeling behavior from the skin.
For this reason, the present state of the art is to use silicone gel adhesives for such applications. The advantage of these adhesives is that even after a long wearing period, they can be peeled from the skin easily and without skin damage. Thus U.S. Pat. No. 4,921,704 describes a wound dressing for exuding wounds, consisting of a porous adhesive layer based on a silicone gel adhesive, and an external absorption layer. U.S. Pat. No. 5,635,201 describes the production of a wound dressing by application of a pressure-sensitive silicone gel adhesive layer to a porous substrate with retention of the porosity. Disadvantages of these solutions, as well as the elevated costs, are the lower bond strength as compared with acrylate-based pressure-sensitive adhesives, and the very low water vapor permeability. A consequence of this is that pressure-sensitive adhesive products based on silicone gel adhesives cannot be applied over their full area to the human skin, since otherwise, as a result of the absent breathability of these adhesive films, macerations may occur to the skin, especially in the course of prolonged wearing periods. From a technological standpoint, production of the interrupted layers of adhesive with these pressure-sensitive adhesives is very complicated, and has the effect of further impairing the bond strength in comparison to acrylate-based pressure-sensitive adhesives.